Oil atomizing double vortex burner



Sept. 17, 1957 J. A. TE NUYL 2,806,517

on. ATOMIZING DOUBLE VORTEX BURNER Filed July 28, 1954 4 Sheets-Sheet 1lnvzni'or: Johannes 'a No@ MM. www

His M'Torneg Sept. 17, 1957 J. A. TE NUYL 2,806,517

op; ATOMIZING DOUBLE voRTEx BURNER Filed July 28, A1954 4 sheets-sheet 21 f l //////////////////////////Y///////////////4 A FneurzE 3 Jchannes'Aie Nuql Sept- 17, 1957 J. A. TE NUYL.. 2,806,517

01x. AToMlzING DOUBLE VORTEX BURNER Filed July 28, 1954 4.Sheets-Shae+.3

INVENTOR Johannes Ale Nuyl BY @M/ww HIS ATTORNEY Sept. 17, 1957 J. A. TENUYL OIL. ATOMIZING DOUBLE VORTEX'BURNER Filed July 28, 1954 4Sheets-Sheet 4 XOE BIV NI BHUSSIHd HIV Johannes A.\e Nuyl HIS ATTORNEYUnited States Patent@ OIL ATOMIZING DOUBLE VRTEX BURNER Johannes A. teNuyl, Delft, Netherlands, assigior to Shell Development Company, NewYork, N. Y., a corporation of Delaware Application July 28, 1954, SerialNo. 446,256

Claims priority, application Netherlands November 16, 1950 Thisapplication is a continuation-in-part of application Serial No. 255,307,tiled November 7, 1951, now abandoned.

This invention relates to a device for burning fluent, e. g., liquid,pulverulent, and/or gaseous fuel and has a high effectiveness not onlywith light fuels but also with heavy fuels, such as viscous residualoils, including tars and asphalt. The invention resides in theparticular combination and arrangement of the elements of theinstallation, including a combustion chamber, means for imparting arotary movement to combustion air and for forming a rotating current orannulus of air, and a huid pressure atomizer for discharging the fueloutwardly into the rotating annulus. For effective combustion resultingin high efficiencies, it is necessary to atomize the liquid fuel and tobring it into intimate contact with air under such conditions, interalia of temperature, that ignition and combustion take place as quicklyas possible.

Much development work has been carried out in recent years towardimproving the combustion eciency of liquid fuel burners. The usual oilburner is not yet, however, ideal for furnace work, particularly whenheavy or viscous fuels are burned. In general, too little energy isavailable for mixing the fuel with combustion air, so that the flamesare long and, hence, subject to the turbulent currents in the furnacespace, which are uncontrolled in many contemporary furnace designs.Strong radiation from these long flames may cause local overheating andthe uncontrolled movements may shift these hot spots and may causeanother undesirable phenomenon, viz., the impingement of llames on thetubes. Apart from the heat effect, the chemical effect of llameimpingernent such as follows from a succession of reducing and oxidizingatmospheres on the same spot is probably of importance; in

any event, such llames lead to untimely destruction of y the tubes oftube furnaces. It is recognized among operators that oil-fired furnacesmust be operated at capacities that are well below those that can beattained with safety when tiring with gas.

Moreover, known burners have been found to fail in v regard to theeffectiveness with which the liquid fuel is atomized and/ or theintimacy of contact with combustion air, and/or the speed with which theresulting fuel-air mixture is heated to bring about rapid ignition.These circumstances lead to reduced combustion efficiencies. Overallfurnace efliciencies of the furnace and, to some extent, combustione'iciencies, are improved by preheating the combustion air, e. g., byflowing it in heat exchange with the outgoing stack gases, and it hasbeen found to be necessary to use moderately high preheat temperatureswhen burning heavy fuels in known burners to attain reasonablecombustion efficiencies.

It has been found that burners in which the combustion air is admittedtangentially into an air casing, from which casing the air is admittedwith a swirling motion forwardly through an air inlet in the rear of thecombustion chamber, usually show a large air resistance; this indicatesan undesirably large expenditure of energy. As a consequence,

the pressure or the air supplied to the air casing and the energyrequired to force the air through the casing and combustion chamber withsuiiicient velocity to insure eicient operation are unduly high.

The objects of the present invention are to provide a burner having highcombustion eiciency when burning liquid fuels, including heavy residualoils such as asphalt; to provide a burner wherein the combustion airneed not be heated to as high a temperature for a given combustionefficiency as in prior devices or wherein such heating may under someconditions be eliminated; and to provide a burner producing a short andhot enveloped flame and which avoids the long flames and reduces directllame radiation with their drawbacks as noted above, whereby the burnermay be employed to supply heat to a tube furnace at a greater rate ofheat output than is generally possible with the usual oil burner Withoutdamaging the tubes.

It is a further important object of this invention to im* prove burnersof the type specified by giving such a shape to the parts of the aircasing that the flow resistance offered by the latter to the air passingtherethrough is decreased.

It is another and more specic object of my invention to improve theefhciency of the burner construction to obtain the Aminimum pressureloss and therefore reduce the power demand for air requirements.

In summary, according to one feature of this invention, the combustiondevice comprises a combustion chamber that is open at the front and hasa closed side wall and a rear wall, there being an opening in the rearwall the effective area of which is constricted relatively to thediameter of the combustion chamber and which establishes communicationwith an air chamber, the air chamber having peripheral air supply meansor openings, such as tangential slots, for admitting air with a rotarymotion to form an advancing rotating current or annulus of air that isintroduced into the combustion chamber forwardly through said opening,and a fluid pressure oil atomizing nozzle for discharging the fueldivergingly into the annulus. lt is important that the axial length ofthe side wall of the combustion chamber be in excess of 0.8 times theinside diameter of the combustion chamber measured at the rear, e. g.,from 0.8 to 1.5 times the inside diameter. The opening in the rear walland the front end of the air casing together form an air inlet which isadvantageously circular and best results are obtained when the diameterthereof is from 0.15 to 0.45 times the diameter o f the combustionchamber, but a somewhat larger range of air inlet sizes, such as from0.25 to 0.67 times the diameter of the combustion chamber, can be used.The closed side walls of the combustion chamber are advantageously madeof refractory material; the combustion chamber, the air inlet at therear wall and the air chamber are all substantially formed as surfacesof revolution, and the side walls of the combustion chamber aresubstantially tubiform, i. e., they do not diverge greatly toward thefront and may be cylindrical.

According to one specic aspect, the invention resides further in aspecial relation between the combustion chamber, the air chamber, theeffective opening in the rear wall of the combustion chamber thatconstitutes the air inlet to the chamber, and the atomizing nozzle, aswill be explained hereinafter. Briefly, the effective opening in therear wall is smaller than the internal diameter of the main portion ofthe air chamber so as to form a throat or constricted passageway betweenthe chambers. The fluid pressure atomizing nozzle in this specialrelation may be of any suitable type that emits a hollow diverging,substantially conical spray of .atomized liquid fuel; it is situated ator near the central axis of the air chamber and back from the rear wallof the combustion chamber Patented Sept. 17, 1957 at the' distancerequired to` cause the conical spray to pass close tothe wall of thethroat without touching it, the spray cone angle being wide enough tocause the cone to intersect the side wall of the combustion chamber. ltshouldl be understood that reference is herein made to the spray cone(as distinguishedl from the conical spray) asa geometrical shapewithoutimplying that the oil drops actually impinge against the chamber wall.By making the side wallsof the combustion'chamber suliici'ently long in.relation to the inside diameter of the combustionchamber as explainedabove, one insures the formation therein of double flame vorticesadjacent the opening in the rear wall, including an inner eddy or whirlinside of the conical spray andan outer eddy or whirl betweeny burnersthat depart from: these relations, asubstantially n cone-shaped airguide. is provided coaxially within the air casing with the narrowerpart of the guide near. the atomizing nozzle and the wideningpartextending axially in a direction away fromA the. combustion chamber overat least the major portion of the axial extent o-f the air casing thatis provided with tangential air inlets. This guide is formed as asurface of revolution and forms a radially inner boundary for theannulus of rotating air that is introduced from the tangential airinlets and thereby prevents the formation of energy-consuming eddies. ltWill be understood that the cross section of the annular space leftwithin the air casing between the periphery thereof andthe air guideincreases in the axial direction toward the air inlet to the combustionchamber, so as to provide an annular air flow channel of graduallyincreasing cross-sectional area; this increase in area is in conformityto the increase in the quantity of air flowing axially through thechamber. The latter increase is caused. bythe intiux of air through thetangential inlets over the entire axial extent that is provided withsuch inlets. Thus, the provision of the cone tends to reduce variationsin the axial How rate of the air over the air casing, and to eliminatedead angles or pockets where eddies are apt to occur.

The air guide need not be precisely a frustum` of a cone; an air guideformed as a surface of revolution generated by a. generatrix that isslightly curved in either direction may also be used. An air guidecurved outwardly (convex away from the axis) has been found to give verygood results.

As a further means of reducing the iiow resistance of the air casing,the tangential air inlet may be formed between tangentially directedstream-lined blades that constitute the outer wall of the air casing.

The manner in which the various elements cooperate to achieve theobjects of the invention will be explained further with reference to theaccompanying drawings forming a part of this speciiication andillustrating certain specific embodiments according to the invention,wherein:

Figure l is a vertical longitudinal section through one embodiment of aburner according to the invention;

Figure 2 is a transverse section taken on line 2 2 on Figure l;

Figures 3 and 4 are vertical longitudinal sections through two differentembodiments showing modifications;

Figure 5 is a transverse section taken on line 5-5 on Figure 4;

Figure 6 is a transverse section similar to Figure 5 showing analternative construction of the air vanes; and

Figure 7 is a graph showing the effect of the air guide.

Referring to Figures l and 2 in detail, there is shown a substantiallycylindrical combustion chamber 10, the walls El of which are made ofrefractory material having the relative dimensions of length to diametershown and provided with an annular ridge 12 forming part of the rearwall of the combustion chamber. An air casing 13 is disposed in the rearof the combustion chamber in axial alignment therewith and defineswithin itself an air chamber communicating atI the open front thereofwith the combustion chamber. The air casing is closed at the rear by awall IA and the outline of the casing is mainly cylindrical, theperipheral side wall being provided with a plurality ofcircumferentially spaced tangential air inlet slots i5 that are delinedby tangentially disposed walls may have outwardly enlarged mouthpieces1.6. The air casing, therefore, constitutes a generally cylindricaltuyere. The rear portion of the air casing is enclosed by an air box 17having an inlet ductl .for admission of combustion air under suitablepressure which may, for example, be of the Order of l0 to 20 inches ofwater when the burner is operating under full load.

It is highly advantageous to shape the air casing with a constriction atthe front providing an orifice 19 that reduces the effective area. oftheopening in the wall 12 and constitutes the air inletV to' the`combustion chamber. Owing to the tangential entry ofthe air through theslots into4 the air chamber, the air moves rotatingly within the airchamber as an annulus toward the orifice if?, and since the diameter ofthis orifice is smaller than that of the slotted part of the air casing;the rotational speed of the air increases as the air Hows into` theorifice. Thus, assuming that friction can be neglected, thecircumferential velocity component is theoretically inverselyproportional to the radius on which the air moves, so that when thediameter of the-orifice 19is half of that of the slotted part, thecircumferential velocity of the air at the edge of the orifice is twicethat of the air entering the air chamber through the slots. In general,it is preferred to have F, thediameter of the slotted part of thecasing, at least 1.5 times C, that of the orifice, c. g., 2.25 timessuch diameter as in the illustrated embodiment, ratios smaller thanabout 3 being preferred. The orifice 19 constitutes an opening in therear wallI of the combustion chamber, which wall is made up mainly ofthe annular ridge 12, and in part by the air casing. This opening shouldpreferably havea diameter related to D, the diam-V eter of thecombustion chamber as previously stated, e. g., it may be 0.42 timessaiddiameter as-shown. It is evidentl that the air advances as a rotatingannulus and is admitted forwardly into thev combustion chamber at themargin of the orifice, which is spaced inwardly from the side wall ofthe combustion chamber.

A tubular atomizer-holder 20 extends inv through the air box 17 and rearwall 14 andA carries a fluid pressure atomizer Ziat the front endthereof,.the atomizer being of any suitable type emitting a hollowconical' spray 22,V the liquid fuel being admitted under pressure at 23.Although an atomizer operating exclusively by fuelv pressure is to bepreferred, because a tine spray can thus be obtained in a simple manner,it is also possible to. use

'an auxiliary atomizing iiuid, such asY air or. steam,..on`

condition that the resultant spray is a hollow, substantially conicaljet. and forming no part of this invention, no further descriptionthereof is deemed to be necessary herein; one form. of atomizer usingonly the pressure of thel fuelfor atomization is disclosed in U. S;Patents Nos. 1,007,793' and 2,323,001, and a form employing. steam underpressure for. atomization is shown in U. S. 1,980,132. The term' iiuidIpressure atomizing'nozzle, therefore7 is used generically to denotenozzles wherein atomization is effected by the pressure of any iiuidl:

supplied to the nozzle.

The atomizer 2l is situated at such a pointin theair chamber that. theconicalV fuel. spray delivered. by the` atomizer enters the combustionchamber near the edge-z Such atomizers being known per se,.

i of the orifice 19 without actually impinging against it.` ln general,it was found to'be important to cause E, diameter of the conical sprayat the transverse plane at which the spray comes closest to the orificeedge, e. g., in the plane, where the spray emerges from the opening inthe embodiment shown, to be between 0.85 and 1.0 times the diameter ofthe orifice in the same plane, e. g., C in the embodiment shown. ltshould be noted that this does not require that the apex angle 0 of theinitial spray be as small as that required by the Equation 2 A tan g=0 Abeing the backward displacement of the atomizer from the forward planeof the orifice, for the reason that the rotating air column deforms thespray so as to diminish the cone angle. The cone angle must be wideenough to make the spray cone, when extended beyond the orice, intersectthe side wall 11 of the combustion chamber.

When the device is placed into operation the spray of fuel passing theedge of the orifice 19 is seized extremely forcibly by the rotating airannulus entering the combustion chamber 1t) through the orifice and avery intimate mixing of the fuel and air takes place, which promotesignition and combustion in the combustion chamber. The wall of thecombustion chamber, which is hot when the device is in operation,imparts heat to the fuel by radiation and thus promotes evaporation,vaporization and ignition and combustion of the latter. Furthermore,however, the shape of this chamber is such that, as indicated in thedrawing, both inside and outside the fuel cone torus-like vortices orwhirls are formed, as indicated at 24 and 2S, respectively, in thedrawing. These annular vortices are situated on the inside and outside,respectively, of the air annulus and extend close to the opening in theorifice. Of these, particularly the outermost whirl 2S leads an alreadyburning mixture back to the place where ignition of the newly admittedfuel is to take place and thus promotes rapid ignition of the fuelentering the combustion chamber. The constriction between thelcombustion and air chambers, formed mainly by the annular ridge 12, istherefore important not only for obtaining a high rotational airvelocity but also for a quick propagation of the ignition, whilst italso prevents incompletely burnt particles from the combustion chamberfrom returning to the air chamber, where they would cause a coke depositto be formed upon the cold parts. The passage of the conical oil sprayclose to the orifice wall is important to insure good mixing and furtherto form a screen preventing the influx of flames and inccmpletely burntparticles into the part of the air chamber behind the spray. The flamecharacteristics described are the result of arranging the combustionchamber and the opening in the rear wall thereof with the dimensionalrelations indicated above.

in practice, it has been found that the ratio of L, the length of thecombustion chamber side wall, to D, the diameter at the rear, isadvantageously close to one. The intensive propagation of the combusionprocess causes it to take place almost entirely inside the combustionchamber this is particularly important where it is undesirable that thepart to be heated should be exposed to intensive ame radiation. This mayoccur, for instance, in tubular stills for heating liquid hydrocarbonsor other liquids, where local overheating of a tube by fierce nadiationmay cause cracking of the hydrocarbons or decomposition or undesiredchemical reactions within the liquids, and thereby give rise to internaldeposits of coke and the like, diminished cooling of the tube at thatpoint, increased overheating and, finally, burning through the tube. Theshort, compact form of the ame has a further advantage where it isdesired `to limit the space required for combustion as much as possible,for example, in gas turbine installations.

lt has been found that a fur-ther advantage of the constructiondescribed is that combustion can be effected with a decreased quantityof excess air, that is, with a higl1' efc1ency', `the CO2 content of theflue gases can with this" burner be increased almost to the theoreticalmaximum. The device is also very suitable for automatic operation. Theatomizer holder 2t) may be surrounded by a burner tube Z6 providing anannular space -to which combustion gas can be admitted at 27. This gascan 'be discharged through 'openings 2S near the atomizer. It has beenfound that a combustible gas can ybe `burned either together with aliquid fuel or separately. The gaseous fuel can be used when there is atemporary shortage of liquid fuel.

Referring to Figure 3, showing a modified construction, like referencenumbers indicate like parts. This construction differs from thataccording to Figures l and 2 mainly in that the air casing 13a is formedas a cylindrical tuyere having three longitudinally displaced rings ofblades 15a, l.

15b and 15C, providing tangential slots to admit air over a greaterlength thereof. These blades may, for example, be stamped out of acylinder and each blade may be flat. The rear end of the casing isclosed by a wall 14a and the forward part of the casing is constrictedto form an orifice 19a that limits the effective area of the opening inthe wall 12 and constitutes the air inlet to the combustion chamber. Theair nose 29 or front of the air casing is sealed to the combustionchamber by an annular ring or collar 30 of refractory material. Astepped trap skirt 31, open at the rear, is mounted about the air casingand has three portions vof progressively small-er diameters, from rearto front, surrounding the three sets of slots, and finally converges tothe diameter of -the air casing. By the use of a stepped trap skirt thecombustion air may be distributed along the length of the air casing.The operation lof this embodiment is like that previously described.

Referring to Figures 4 and 5, showing a preferred construction andwherein like reference numbers denote parts previously described forFigures 1 and 2, the combustion chamber 10 has a rear wall including anlouter annular, slightly conical par-t'12, leaving a circular opening atthe center. The air casing, which is aligned on a common axis with thecombustion chamber and the opening in the rear wall and is likewiseformed as a body of revolution, com'- prises a plurality of longitudinalblades 32 that are fixed to end rings 33 and 34 and are distributed atuniform circumferential intervals and disposed tangentially with re#gard to the air chamber so as 4to leave narrow tangential air slots 35lbetween the blades through which air enters from the air box 17in-tothe cham-ber with a vswirling motion. The stepped trap skirt 31 ofFigurev'aJ is omitted. Forwardly -of the blades is a constricted airnose 36 providing a throat or orilicial constriction 19 that constitutesthe air inlet to the combustion chamber and is joined .to For conthebladed part by an imperfora-te tube 37. venience in mounting, the aircasing may 'be fabricated in two separate sections, the forward partcomprising the air nose and tube 37, being bolted to a plate 38 mountedon the rear furnace wall; the rear bla-ded tuyere part has fixed theretoa sleeve 39 which is slid into the tube 37, the bladed part beingthereafter secured to the rear wall 40 of the air box as describedbelow. To protect the air nose from intense radiation, it is desirableIto place a collar 30 of refractory material about it. The air nose,when thus in position, forms a part of the rear wall of the combustionchamber and .the orice at the front of the air nose constitutes theopening in the rear combustion chamber wall.

The air casing carries a tube 41 welded to the end ring 33 and to anannular flange ring 42 that engages a frame 43 mounted in the wall 40.The flange ring is securedin position by a closure plate 44 which isclamped in position by clamps 45.V The closure plate closes the rear ofthe air chamber and carries a support sleeve 46 at the axis of the air`chamber within which is mounted the burner tube 26 withva close slidingt; the latter may besecured in adjusted axial position by a set screw47. The tube 26 carries concentrically therein the fuel supply andatomizer holder tube-20 which carries the fluid pressure atomizer 21 atthe front end thereof and which is supplied with liquid fuel at 23. Thetube 20 is spaced from the burner tube 26 to; provide an annular passagefor combustible gas which may be supplied at 27 and discharged at 2Saround the atomizin-g nozzle. The air inlet duct 18 may be provided witha damper 48. A lighter .tube 46 traverses the walls 12, 38 and 40; thismay also Ibe used for inspection.

As is shown in Figures 4 and 5, the blades or vanes 32 in thisembodiment differ from those of the previous embodiments in that theyhave stream-lined or airfoil shapes, the cross section of each vane`being rounded at the outer end, attaining a maximum thickness near theouter end, and. having a longer inner portion ycoming substantially toan edge with4 a small taper angle. Such a shape effectively reduces Itheresistance voffered by the vanes to the air flowing into the airChamber.

According to a variant shown in Figure 6, the blades 32a are curvedconcavely in a common circumferential direction and are overlapped,thereby providing tangential passages 35a that are bounded on the innerand outer sides by smooth walls. This has the advantage over theembodiments of Figures 1-3 of introducing the air into the air casingwith less turbulence and more nearly tangentially to the slotted part ofthe air casing, thereby achieving greater angular mo-vement. Further, asdistinguished from the embodiment 'of Figure 3, it will be noted that asmaller number of tangential inlets may be used. Although less costlythan the airfoil blades of Figures 4 and 5, the curved blades 32a entailsomewhat higher air resistances.

The air .casing of Figures 4 and 5, as well as that of Figure 6,contains a truste-conical air guide S that surrounds. and is coaxialwith the burner tube 26. The smaller, front end of the air guide issupported by the tube 26 and is, for best results, situated close to theatomizer nozzle 21, as shown; the invention7 however, includes variants,e. g., those wherein the front of the air guide is set back from theatomizer. The air guide widens toward the rear and extends over themajor part of and, preferably, over the full axial extent of the slots35 or 35a, the rear end is supported by the end ring 33, to which it canbe welded, so as to close the rear end of the air chamber. The air guide50 may, of course, have other shapes, e. g., be trumpet-shaped, and neednot be sealed to the end ring 33. Between the air guide 5.0 and thevanes 32 or 32a there remains an annular air space that is coaxial withthe orifice 19 and the cross-sectional area of which increases towardthe open, front end of the air casing, somewhat in correspondence withthe increase in the amount of air passing through the said space at itssuccessive cross sections. lt will be understood that this increase inthe amount of air is due to the distribution of the inowing air over thelengths of the slots 35 or 35a. The cone 50, by guiding the forwardlyadvancing and rotating annular air column in the air casing, whichprogressively diminishes the internal dimen- Sion of the annular aircolumn, and by preventing the establishment of energy-consuming eddies,reduces the resistance the air casing offers to the passing air. Theair, having received a tangential component upon entering the air casingthrough the slots, swirls with a progres.- sively increasing angularvelocity as it moves closer to the axis, and the reduction in energyloss promotes a more intensive swirl, which results in improved mixingwith the fuel which is sprayed from the atomizer. The preferredconstriction of the air casing beyond the slotted sportion of the casingcontracts the external dimension of the annular air column just prior toemerging through the orifice 19 and thereby causes an increase in theangular velocity of the air. The emergence of the swirling air throughthe air inlet to the combustion chamber and the formation of vorticesare as described above.

Although the conical air guide was described particularly with referenceto one type of burner, it should be understood that it is not limitedthereto. For example, the air guide may be employed to advantage withair casings of the types shown, for example, in Figure 3, as well as in,burners that do not employ burner tips constituted by atomizers forspraying liquid, e. g., wherein gas is burned, and/ or wherein theburner tips are not located within the air casing as shown.

The improvements realized by the improved air casings are indicated inFigure 7 which shows the relations between the air pressure in the airbox 17 and the rate of air iiow through the air casing. Air pressures ininches of water are plotted as abscissae and the squares of the air flowrates in cubic feet per second are plotted as ordinates. Curves A and Bare for air casings without and with an air guide, respectively,provided with peripheral tangential vanes in the shape of plates; curvesC and D are for air casings without and with an air guide, respectively,provided with tangential stream-lined blades in the shape of airfoils,as shown in Figures 4 and 5. Curves B and D apply both to straight andslightly convex (trumpet-shaped) cones. It is evident that aConsiderable improvement in the air pressure is effected by each of theimprovements, viz., by the use of stream-lined blades and by the use ofthe conical air guide.

The relative dimensions shown for the embodiment of Figures 4 and 5 areas follows: L:D=:l.0; C:D=0.23; F:C=l.6. Moreover, the atomizing nozzle21 is positioned to cause the spray cone 22 to make the ratio E:Cgreater than 0.85 and to intersect the combustion chamber wall 11 alonga circle which is displaced a distance H from the mouth of the chamber,the ratio HzL being in this instance 0.39. As was indicated previously,it is advantageous for promoting the swirls and for effecting rapidheating of the fuel and generating a short hot flame to have the coneintersect the combustion chamber side wall in the forward half of thechamber, whereby the ratio H:L should be less than 0.5.

Summarizing the optimum dimensional relations indicated heretofore inthe text:

I claim as my invention:

l. A combustion device `for liquid fuel comprising, in combination: asubstantially tubiform combustion chamber having an enclosing refractoryside Wall formed with a surface of revolution about the chamber axis andopen at the front7 the axial length of said side wall being equal to atleast 0.8 times the diameter of the chamber measured at the rear, and arear wall having an opening therein at said axis; an air casing in rearof said rear wall, said air casing being closed at the rear and open atthe front, the front of the air casing and the said opening in the rearwall providing a circular air inlet to the combustion chamber, said airinlet having a diameter between about 0.l5 and 0.67 times the saiddiameter of the combustion chamber, said air casing having an annularside wall the axis of which is aligned with said axis, said side wallbeing formed with a plurality of circumferentially spaced wall elementsdefining tangential air inlet passages for the inward flow of airrotatingly about said axis and the forward discharge of the air throughsaid air inlet into the combustion lchamber as a rotating annulus spacedfrom the side wall of the combustion charnber, the diameter of saidannular side wall of the air casing being at least 1.5 times thediameter of said said air inlet; an air box surrounding the annular sidewall of the air casing; and, Within the air casing, a Huid pressureatomizing nozzle of the type that emits a hollow, diverging spray ofatomized oil, said nozzle being displaced rearwardly from the said airinlet so as to discharge a spray of oil outwardly into said rotatingannulus and forwardly through said air inlet with the diameter of thespray cone, measured in the transverse plane of closest approach to theedge of the said inlet, between about 0.85 and 1.0 of the diameter ofthe inlet, measured in the same plane, and with the cone of the spray,when projected, intercepting said side wall of the combustion chamberforwardly of said rear wall, whereby a flame formed by igniting theresulting inammable mixture of air and fuel will form vortices of flamegases within the combustion chamber both adjacent the said inlet betweenthe spray cone and the side wall of the combustion chamber and alsowithin the spray cone for rapidly heating the atomized fuel andstabilizing the iiame against extinction.

2. A combustion device as claimed in claim 1 wherein the diameter of theannular side wall of the air casing is in the order of 1%. to 3 timesthe diameter of the said air inlet, and the axial length of thecombustion chamber is in the order of 0.8 to 1.5 times the diameter ofthe chamber measured at the rear.

3. A combustion device according to claim 1 wherein the atomizing nozzleis disposed to cause the cone of the spray, when projected, to intersectthe side wall of the combustion chamber in the forward half of thecombustion chamber.

4. A combustion device according to claim 1 wherein the tangential airinlet passages in the air casing are situated in a rearward part of thecasing, said casing having a forwardly gradually converging imperforatesection between the said passages and the front end of the casing.

5. A combustion device according to claim 1 wherein said annular sidewall of the air casing comprises a plurality of stream-linedtangentially disposed blades that are shaped as airfoils and constitutethe said wall elements defining the air inlet passages.

6. A combustion device according to claim 1 wherein the air casingcontains a concentric, substantially conical air guide disposed with thesmaller end thereof toward said combustion chamber and widening in theaxial direction away from the combustion chamber over at least a majorportion of the axial extent of the casing side wall that is providedwith tangential air inlet passages.

7. A combustion device for uid fuel comprising, in combination: acombustion chamber having an enclosing refractory side wall and beingopen at the front; an air casing defining within itself a peripheryunobstructed air chamber and situated in rear of said combustionchamber, the rear of the combustion chamber and the front of the aircasing being in communication through an unobstructed air inletpassageway substantially at the axis of the air casing, said air casinghaving an annular side wall that has a diameter in excess of the saidair inlet passageway and includes a wall structure providingcircumferentially spaced, tangential air inlets disposed for the inflowof air along the length of the side wall rotatingly about the axis ofthe air casing and the forward discharge of the air into the combustionchamber as a rotating annulus; a fuel nozzle within the air casingdirected to discharge fuel outwardly into said rotating air annulus andforwardly into the combustion chamber through said air inlet opening; asubstantially conical air guide concentric within said air casing havingthe smaller end thereof contiguous to said fuel nozzle and widening inan axial direction away from the combustion chamber over at least amajor portion of the axial extent of the air casing side wall that isprovided with tangential air inlets and a closure wall at the rear ofsaid air guide, whereby all of the air flows outside of said air guide.

8. A combustion device comprising, in combination: a substantiallytubiform combustion chamber having an enclosing refractory side wallformed with a surface of revolution about the chamber axis and open atthe front, the axial length of said side wall being equal to a least 0.8times the diameter of the chamber measured at the rear, and a rear wallhaving an opening therein at said axis; a casing for a gaseous medium inrear of said rear wall, said casing being closed at the rear and open atthe front, the front of the casing and the said opening in the rear wallproviding a circular inlet to the combustion chamber, said inlet havinga diameter between about 0.15 and 0.67 times the said diameter of thecombustion chamber, said casing having an annular side wall, the axis ofwhich is aligned with said axis, said side wall being formed with aplurality of circumferentially spaced wall elements defining tangentialinlet passages for the inward flow of said medium rotatingly about saidaxis and the forward discharge of the medium through said inlet into thecombustion chamber as a rotating annulus spaced from the side wall ofthe combustion chamber, the diameter of said annular side wall of thecasing being at least 1.5 times the diameter of the said inlet; a supplybox for said medium surrounding the annular side wall of the casing;and, within the casing, a uid nozzle of the type that emits a hollow,diverging cone of fluid, said nozzle being displaced rearwardly from thesaid inlet so as to discharge a spray of uid outwardly into saidrotating annulus and forwardly through said inlet with the diameter ofthe fluid cone, measured in the transverse plane of closest approach-tothe edge of the said inlet, between about 0.85 and 1.0 of the diameterof the inlet, measured in the same plane, and with the cone of the Huid,when projected, intercepting said side wall of the combustion chamberforwardly of said rear wall, whereby a flame formed by igniting aninliammable mixture of said gaseous medium and fluid will form vorticesof flame gases within the combustion chamber both adjacent the saidinlet between the fluid cone and the side wall of the combustion chamberand also within the uid cone for rapidly heating the materials chargedto the combustion chamber and stabilizing the ame against extinction.

References Cited in the le of this patent UNITED STATES PATENTS1,665,800 Strachan et al Apr. 10, 1928 1,943,083 McDonald et al. Jan. 9,1934 2,464,791 Bonvillian et al. Mar. 22, 1949 2,539,165 Saha Jan. 23,1951 2,560,074 Bloomer July 10, 1951 2,678,615 Soderlund May 18, 1954FOREIGN PATENTS 1,062,062 France Apr. 20, 1954

